Recovery of useful product from spent doctor



Oct. 13, 1953 J. B. HOLTZCLAW 2,655,483

RECOVERY OF USEFUL PRODUCT FROM SPENT DOCTOR Filed July 25, 1952 7 DodToU Clbborn e5 Patented Oct. 13, 1953 RECOVERY OF USEFUL PRODUCT FROMSPENT DOCTOR John B. Holtzelaw,

Standard Oil ration of Delaware Application July 23, 1952, Serial N o.

Roselle, N. J., assignor to Development Company, a corpo- 3 Claims. (Cl.252183) to form disulfides and The plumbite solution lead oxide insodium is prepared by dissolving hydroxide as follows:

(Sodium Plumbite) PbO+2NaOH- Na2PbOz+H2O Upon the addition of sulfur therelatively innocuous disulfides are formed and lead sulfide isprecipitated as follows:

In these reactions the spent doctor solution is regenerated as follows:

However, in time sodium thiosulfate tends to build up in the spentdoctor by the action of oxygen from the air on the sodium sulfide.

tic mercaptans to polysulfides.

e spent doctor solution withdrawn from the heating oil treatmentcontains an appreciable removed from propyl alcohol.

The process of the present invention may be more fully understood byreference range is introduced mto treating zone I by means of feed line2. Fresh caustic is introducedinto zone I by means of line 3, whilespent caustic is removed by means of line 4. The treated oil is zone Iby means of line 5 and inof line I0 esh caustic is introduced into zone9 by means of line H and withdrawn by means of line 12 The treated 011is removed from zone sodium thiosulfate. In accordance with the presentinvention, so-

sodium sulfide and sodium thiosulfate, and a sediment of PbS is removedby means of line 29.

This solution is very adaptable for the manufac turing of paper afterthe recovery of traces of alcohol and filtering or centrifuging toremove the PbS.

The process generally is concerned with the handling of a spent doctorsolution, particularly a spent doctor solution segregated from a naphthatreating operation followed by subsequent heating oil operations. Thetreating agent comprises sodium bisulfide and a low molecular weightalcohol, preferably isopropyl alcohol. The amount of sodium bisulfidepresent may be varied appreciably in the treating solution butispreferably in the range from about -12% by weight. Approximately 10%by volume of spent caustic solution containing the sodium bisulfide isadded to zone 18 by means of line H). The quantity of alcohol added alsomay vary appreciably but is in the range from 30 to 50% .by-volume. Theconcentration of the alcohol in the range from 90-95%. What is claimedis: 1. Improved process for the production "of a solution comprisingsodium sulfur salts which comprises contacting a hydrocarbon mixturecontaining mercaptans and boiling in the motor fuel carbon mixturecontaining mercaptans and boiling in the heating oil 'boilin'g range,withdrawing the spent doctor and contacting the same with an alkalimetal bisulfide and a low molecular weight alcohol, whereby three phasesform. withdrawing the intermediate phase and dislt'i-l ling the same,removing alcohol overhead and removing a bottom fraction comprisingsodium sulfur. salts.

2. Process as defined by claim 1 wherein the b'isulfide is sodiumbisulfide and wherein said alcohol comprises isopropyl alcohol.

3. Process as defined by claim 2 wherein the amount of alcohol employedis from about to by volume based upon the volume of spent doctorsolution and wherein the concentration of the alcohol is in the rangefrom'about to JOHN B. HOLTZC-LAW.

References Cited in the 'file of this patent UNITED STATES PATENTS

1. IMPROVED PROCESS FOR THE PRODUCTION OF A SOLUTION COMPRISING SODIUMSULFUR SALTS WHICH COMPRISES CONTACTING A HYDROCARBON MIXTURE CONTAININGMERCAPTANS AND BOILING IN THE MOTOR FUEL BOILING RANGE WITH A DOCTORSOLUTION, THEREAFTER USING SAID DOCTOR SOLUTION TO CONTACT A HYDROCARBONMIXTURE CONTAINING MERCAPTANS AND BOILING IN THE HEATING OIL BOILINGRANGE, WITHDRAWING THE SPENT DOCTOR AND CONTACTING THE SAME WITH ANALKALI METAL BISULFIDE AND A LOW MOLECULAR WEIGHT ALCOHOL, WHEREBY THREEPHASES FOR WITHDRAWING THE INTERMEDIATE PHASE AND DIS-